On 8/28/20 10:26 AM, antlists wrote:
On 28/08/2020 03:31, R. Ramesh wrote:
I want to build new raid using the 16/14tb drives. Since I am
building new raid, I thought I could explore caching options. I see a
mention of LVM cache and few other bcache/xyzcache etc.
Is anyone of them better than other or no cache is safer. Since I
switched over to NVME boot drives, I have quite a few SATA SSDs lying
around that I can put to good use, if I cache using them.
Sounds like a fun idea. Just make sure you're getting CMR not SMR
drives, but I'm not aware of SMR that large ...
Hopefully I'm going to do some work on it soon, but look at
dm-integrity to make sure you don't get a dodgy mirror. You can add
dm-integrity retrospectively, so if you leave a bit of unused space on
the drive, I think you can tell dm-integrity where to put its checksums.
Cheers,
Wol
Yes, no SMR. I plan to get only enterprise helium drives (seagate exos
X14 or X16).
I googled on RAID cache performance. I did not get too many interesting
hits. A couple that find seem to indicate that LVM cache shows no
performance improvement. Can't understand why. May be SATA limits (SSD =
500MB and disk could be as high as 200M and with raid1 that might go up
as we have two disks to read etc)
I am mainly looking for IOP improvement as I want to use this RAID in
mythtv environment. So multiple threads will be active and I expect
cache to help with random access IOPs.
Regards
Ramesh
